


Undertale Reader-Insert One-Shots

by RosieSampaguita



Category: Undertale (Video Game)
Genre: Alternate Universe - Echotale (Undertale), Alternate Universe - Horrortale (Undertale), Alternate Universe - Lamiafell (Undertale), Alternate Universe - Mafiafell (Undertale), Alternate Universe - Mafiatale (Undertale), Alternate Universe - Swapfell (Undertale), Alternate Universe - Underfell (Undertale), Alternate Universe - Underswap (Undertale), F/M, Gaster Papyrus (Undertale), Gaster Sans (Undertale), Horrortale Papyrus (Undertale), Horrortale Sans (Undertale), Lamiafell Papyrus (Undertale), Lamiafell Sans (Undertale), Mafiafell Papyrus (Undertale, Mafiafell Sans (Undertale), Mafiatale Papyrus (Undertale), Mafiatale Sans (Undertale), Swapfell Papyrus (Undertale), Swapfell Sans (Undertale), Underfell Papyrus (Undertale), Underfell Sans (Undertale), Underswap Papyrus (Undertale), Underswap Sans (Undertale)
Language: English
Status: In-Progress
Published: 2019-12-19
Updated: 2019-12-19
Packaged: 2021-02-26 04:07:01
Rating: General Audiences
Warnings: No Archive Warnings Apply
Chapters: 7
Words: 2,910
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/21857302
Author URL: https://archiveofourown.org/users/RosieSampaguita/pseuds/RosieSampaguita
Summary: A collection of Sans/Reader and Papyrus/Reader fics I've written for my Tumblr imagines blog.
Relationships: Gaster!Papyrus/Reader, Papyrus (Echotale)/Reader, Papyrus (Horrortale)/Reader, Papyrus (Lamiafell)/Reader, Papyrus (Mafiafell)/Reader, Papyrus (Mafiatale)/Reader, Papyrus (Swapfell)/Reader, Papyrus (Underswap)/Reader, Papyrus (Undertale)/Reader, Papyrus (underfell)/reader, Sans (Lamiafell)/Reader, Sans (Mafiafell)/Reader, Sans (Mafiatale)/Reader, Sans (Swapfell)/Reader, Sans (Underfell)/Reader, Sans (Underswap)/Reader, Sans (Undertale)/Reader, gaster papyrus/reader
Comments: 2
Kudos: 49





	1. Underfell Papyrus with an S/O with Low Self Esteem

**Author's Note:**

> I'm open for requests if you have one! Just please look at my profile for the rules

You and Edge were out on a shopping date (THE MANUAL OF CONQUER BY LOVE SAYS THIS RITUAL WILL INCREASE EMOTIONAL TIES AND LOYALTY!!) and he had insisted you put on a fashion show for him.

He had gone crazy, grabbing clothes to create outfits that ranged from biker chick to fairy princess to cozy sweater shirts and sweatpants. And, despite any of your protests, he insisted you try each and every one of the outfits he picked on and give him a fashion show.

Thankfully, this store wasn’t that crowded which allowed Edge to pile up the clothes he accumulated and critique the way the clothes looked on you. (YES, THAT JACKET REALLY BRINGS OUT YOUR EYES!! NO, NO! URGH, THE MANNEQUIN LIED!! THAT COLOR COMBINATION DOES NOT DO YOUR WONDERFUL COMPLEXION JUSTICE!)

As Edge continued his vocal fashion show, a crowd began forming around him. Granted, it wasn’t that big, mainly employees who had nothing better to do and a few customers who found the concept of a skeleton monster giving a fashion show to be fascinating.

As the crowd gathered, Edge paid no attention to them, thinking they were merely there to gawk at him, all his attention was focused on you and finding ways to expand your wardrobe to more than a warm hoodie and several sweatpants and graphic tees.

Inside the changing booth however, you were freaking out. You saw people flocking to your area and you felt your face heat up with embarrassment. You didn’t have the confidence your boyfriend had to strut your stuff in front of strangers, and you felt your anxiety welling up each time you went outside of the changing booth.

“DARLING, WHAT IS TAKING YOU SO LONG?!” Edge cried impatiently, in your mind’s eye you could picture him crossing his arms and pouting, acting like he could puff out his cheekbones.

Normally you’d think his impatience to be adoring, but right now it wasn’t. “E-er, n-nothing, E-Edge!” You squeaked, hiding your face in your hands as you saw the crowd outside. “WELL THEN WHAT’S TAKING YOU? I NEED TO SEE IF THAT SCARF IS UP TO PAR WITH YOUR NATURAL BEAUTY!!”

You felt your face flush as fear spiked inside you. “I-I can’t!!” You shouted suddenly, “WHY NOT?” Edge demanded, you imagined him placing his hands on the hipbones that jutted out from his leather pants.

“I-I just-!” You couldn’t bring yourself to say it. That your low self-esteem was making you hide behind the curtain of the changing booth like it was a bunker. Safe from any judging eyes.

You heard Edge huff loudly before knocking on the wall next to the curtain to alert you of his presence and desire to see you. “ARE YOU DECENT?” He asked, a bit quieter than his normal volume. Taking a shaky hand you pulled the curtain back far enough so your head popped out.

“Y-yeah.” You stammered, cheeks heating up as you realized how closely he was standing to you. “THEN WHY DO YOU REFUSE TO COME OUT?” He questioned, “ARE THE CLOTHES THE WRONG SIZE?”

You shook your head and peered around your skeleton boyfriend.”N-no, love, it’s just…….” You trailed off as you saw two girls whispering at each other, your anxiety immediately accusing them of heckling about you.

You hid your face from them so you could only see Edge “I-I just d-don’t……” Edge gave you a look that mixed concern and frustration. “DON’T WHAT?” He prodded.

You felt your chest sink and your cheeks flush “I-I don’t feel confident.” You said meekly. Edge’s bone brows shot up and concern was the only thing present on his facial features. “I-It’s just………..you have so much self-esteem a-and I just-”  
Edge shook his head and fit his mouth into a tight line. He looked down at the outfit you were wearing. If you had low self-esteem, then he’d help you deal with it. Without warning, Edge threw back the curtain, making you squeal in surprise.

With flourish, Edge loops his arm around your waist and led you out into the center of the crowd. “BEHOLD!!!! THE GORGEOUS AND TALENTED (NAME)!!!” He proclaimed loudly, flaunting you as he strutted into the crowd.

Your face went crimson “E-edge!!!” You cried, tugging on his arm. “What are you doing!?” Edge gave you no response but held you at arms length and began pointing out everything about the outfit that flattered your physical appearance.

By the time Edge had got through with the outfit, the crowd was clapping and a few asked for pictures which Edge had you participate in with his arm wound tight around you.

Once the whole debacle ended, Edge had bought that outfit and your favorite ones from the pile, loudly proclaiming that his EXTREMELY FETCHING AND INTELLIGENT S/O was worth buying a pile of clothes for.

As you exited the store with Edge, your face still on fire, you asked him to explain himself back there. He knew you had issues with large crowds!!

Edge simply gave you that annoying yet swoon-worthy smirk. “YOU ARE MINE, ARE YOU NOT?” He asked simply, your face exploded in another round of fluster “Y-yeah? So?” You asked, trying to keep your composure. “WELL THEN, IF YOU FEEL LOW ABOUT YOURSELF, THEN IT IS UP TO ME TO MAKE YOU FEEL GOOD, YES?”

Your face was on fire and you felt yourself wanting to curl into yourself you were so flustered.

You know that game couples do to try and out fluster each other? Yeah, Edge has now made that his personal goal to make you so flustered you stop functioning daily.


	2. Gaster!Papyrus meets Benedict Cumberbatch

**Summary for the Chapter:**

> Anon: sorry if I'm bothering you, but what if G!Paps S/O got him to meet Benedict Cumberbatch (actor of Sherlock Holmes)?

**Notes for the Chapter:**

> You’re not bothering me at all, sweetheart! I love this ask ^.^
> 
> I'm using Aster as G!Pap's nickname btw

So Aster is the biggest Sherlock Holmes dork, he made his own coat and scarf that perfectly mimicked the one Cumberbatch uses.

And the tall dork would sometimes go around the home trying to analyze everything, and even had you try and dress up in a bunch of different things to try and throw his deductions off.

So when Aster met him, the normally calm and reserved skeleton FLIPPED out.  
He squealed like a child before excitedly going up to Benedict to ask for a hug or handshake and began asking questions a mile a minute.

This sweet beanpole was a bit taller than Benedict but that doesn’t stop him from looking up to the actor.

Aster asked everything from how is it to work as an actor and how to tell a good director from a bad one to how does he like the interpretation of his Sherlock and if he wanted to change anything about how his character or some of the others are portrayed.

(Aster was beyond thrilled that Cumberbatch agreed with him when he mentioned he was disappointed that Irene Adler was reduced to a Complex Seductress instead of a respected mastermind)

But as much as Aster wanted to hang out with Benedict, he knew the actor had other responsibilities and offered to keep in touch.

Imagine his surprise when Benedict contacts him first, the excited bean nearly swooned so hard he lost balance

Also, be prepared to hear nothing but trivia bits about Sherlock Holmes and how much he admires Benedict Cumberbatch because this lovable dork is in complete fanboy mode.


	3. Gaster Bros hear their S/O sing "Remember Me"

**Summary for the Chapter:**

> Anon: Sorry, but I have to ask. What if G!papyrus and G!Sans over heard their S/O singing Remember Me, annapantsu version

**Notes for the Chapter:**

> I JUST LISTENED TO THE ANNAPANTSU VERSION AND I WANNA CRY ALL OVER AGAIN MY H E A R T
> 
> This is Part 1 of the ask, the second half is the next chapter.

**Gaster!Sans (G)**  
G would literally be in tears overhearing that song because the phrase “Remember me” always sounds so soulful and beautiful but painful at the same time and he really loves how the song you’re singing is about remembering someone you love after they’ve been gone.

And considering G has a big fear about forgetting about everyone he’s loved, he gets more emotional during the song than most people would and by the time you hit the chorus the third time he’s humming with you.

When you turn around to see G standing in the doorway, he’s gonna be wiping a few tears and rushing to hug you. He’ll also give you many many soft kisses and tell you “I’ll always remember you.”

 **Gaster!Papyrus (Aster)**  
Aster would have been getting ready to go on a quick camping trip with his brother when he heard you singing that song. At first he thought it was a radio playing because he didn’t recognize your voice being so gentle (he’s used to you shouting your favorite lyrics with enough enthusiasm to cause an earthquake).

Needless to say, this gentleman did a double take when he heard you and nearly started balling when you sang “ For even if I’m far away, I hold you in my heart “.

Aster would probably end up rescheduling the camping trip with his brother because after hearing that song, Aster suddenly needs to spend every single second with his beloved S/O and make as many memories as they can together.


	4. Underfell Papyrus hears his S/O singing Remember Me

**Summary for the Chapter:**

> Anon: Sorry, but I have to ask. What if UF!Papyrus over heard their S/O singing Remeber Me, annapantsu version

**Notes for the Chapter:**

> Continuation of previous chapter

Edge was probably giving Doomfanger a quick grooming (read: luxury spa day complete with homemade cat-safe bath bomb) when he heard you singing. At first he didn’t think much of it as he was used to you spontaneously breaking out into song when you felt like it.

But then he noticed the tone of the song was more melancholy and reminiscent than most songs you’re used to singing and paused his homemade spa day for his prized cat to go find you and figuring out why you were singing.

Edge finds you singing to yourself as you work idly on something in the living room and he suddenly finds himself under a spell. Your singing had always captivated him but the way you softly sang the song but still had tons of emotion behind the simple words suddenly made the edgy skeleton want to curl up next to you and cuddle you for the rest of the day.

The dork will end up spying on you singing until he bursts into tears because of how emotional the song is and when you notice him, he’s just gonna zoom right over to you, throw his arms around your waist and bury his face in your stomach saying “I’ll always remember you and I love you.”


	5. Underfell Bros as Dads

**Summary for the Chapter:**

> lmao-idk-but-aight: (Yeet, it’s the meat, here to skeet skeet) Edge and Red discovering a baby on their doorstep headcanons?? Like a monster baby is just like there and they have to be its dads, what kind of dads would they be?

**Underfell!Papyrus (Edge)**  
Edge would first and foremost be c o n f u s e d.

Whomst thought it was a good idea to leave a BABY all alone? How did this person even know Edge would take care of the tiny thing?!

At first Edge might just go back inside and try to ignore the baby and act like he didn’t see the tiny thing but two steps back towards the kitchen Edge feels it.  
The urge to protecc and care for the smol child.

Edge mutters something about how being a Cat Dad™️ has made him soft and grabs the baby inside the house.

Raising a baby shouldn’t be that hard, right? After all, his brother practically raised Edge with no help and look at how fabulous Edge turned out.

From that moment forward, Edge considers the baby his own and whenever someone asks about how Edge encountered the baby he usually uses a joking answer like “the Stork” or “the baby followed me home and I kept them”.

Very rarely will he tell the truth because he’s scared of the baby’s real family discovering them and taking his adopted child away from him.

Though he won’t object if the child wants to find their parents, Edge just fears he will loose his baby if he isn’t careful.

As to the type of dad Edge would be, Edge would at first be an easily frustrated and clueless dad.

He doesn’t understand why the baby needs so much care and attention and it frustrates him that he can’t understand what the baby needs and wants like he can with Doomfanger.

But once his brother gives him a few tips and Edge checks out some parenting books, he becomes the stay at home dad that makes everyone swoon over.

He will get the kid into physical activities, he wants to make sure the kid can put up a fight and WILL train them despite protests. He will adjust the methods of teaching as needed, but like it or not, his child is going to know how to properly beat up someone in the name of self-defense.

With some practice, Edge becomes an encouraging father, he’s used to only having faults pointed out so it takes him a while to transition from “wow, you weren’t as terrible as I thought you’d be” to “You’ve done very well, I’m proud of you”.

Overall, Edge is a good dad, he just needs some help from his brother, a friend, or a parenting book to keep him focused.

 **Underfell!Sans (Red)**  
Red knows first-hand how hard it is to grow up in a kill or be killed world with no guidance. As soon as he sees the baby on his doorstep he takes it inside.

Since he already raised Edge on his own, Red has a better idea what to do, but since this is a stranger’s baby and not his little brother, Red needs a refresher course in taking care of smol persons.

Red tries to live off his distant memories of raising Edge but eventually goes out and buys a few books and CDs on how to be a good parent.

Turns out those books and CDs are great for putting the baby and himself to sleep.

Red is a more laidback dad, oh sure, he will put in all the effort to torment his child with bad puns and incidental music but Red prefers to let the kiddo make their own decisions as much as possible.

Like Edge, the poor kid isn’t getting out of self-defense lessons but Red’s tactics are a bit more ridiculous. Instead of facing the enemy head on like Edge, Red teaches the kid how to avoid fights and be untouchable but still formidable.

Red discovers early on that being a dad is a lot different than being an older brother so he and his adopted child will have a bit of a rocky relationship at first but they will eventually be best buddies.


	6. Underfell Papyrus Headcanons about helping his wife with body issues

**Summary for the Chapter:**

> lmao-idk-but-aight: (Yo yo yo it’s ya boi) Can I have like maybe some headcanons for Edge if he had a wife with body image issues? Like she doesn’t like her body so he tries to help her like herself.

**Notes for the Chapter:**

> *rubs hands together* Here’s some soft edgy boi coming your way!!

  * Edge at first doesn’t really get it
  * “What do you mean you’re not confident about your body??? You could literally crush half the monsters in the Underground with your thighs if you weren’t so nice!”
  * It takes him a while to understand that you feel insecure about yourself before he starts figuring out ways to help build up your confidence
  * At first it’s mostly just compliments
  * “Your eyes look very radiant today, my mate~”
  * “Have I mentioned the backside of you looks very stunning?”
  * Then he gradually starts pointing out very specific things about you that he notices you felt insecure about
  * “I love how soft you are, you’re like a walking pillow.”
  * He means this in the best way, someone help him
  * “Have I told you I love the way your stretch marks look? They look like scars but ones you’ve earned outside of battle.”
  * “And a few look like tiger strips which are utterly adorable”
  * If you want to change something about you, Edge will be your cheerleader, drill sergeant, and loving servant.
  * “You won’t achieve your goal if you keep letting your knees drop, piCK THEM UP HIGHER LIKE YOU’RE STOMPING ON THE HEADS OF YOUR ENEMIIIESSSS!!!”
  * “You’re doing so well, my beautiful mate, I love you so much, I know you can push yourself harder!”
  * “Do you need water? A massage? One of those heating pads????? yOUR FACE IS ALL RED, TELL ME WHAT I NEED TO DO TO HELP”
  * And God help whoever decides it’s a good idea to try and mock you as you’re dealing with your body image and/or mocking you as you try to change yourself
  * “You wanna say that again about the gREAT AND TERRIBLE PAPYRUS’ BELOVED MATE, YOU CRETIN!?!?!???? I WILL DUST YOU AND SPREAD YOUR ASHES OVER THE GARBAGE DUMP WHERE YOU WERE BORN!!!!”
  * Someone stop him before he hurts himself




	7. Edge with a Lolita S/O

**Summary for the Chapter:**

> lmao-idk-but-aight: tHIRD TIME AROUND IN THESE PARTS!!! So I had yet ANOTHER idea. What if UF Pap had an S/O that was secretly a Lolita and finds out when he sees her with her friends at a Lolita meet up

**Notes for the Chapter:**

> Ehehehehe, *Edge’s voice: CUTE THINGS!!! MY ONLY WEAKNESS!!! I tried making this like a one shot but it always ended with too much awkwardness and never went the way I wanted it to so sorry in advance XD

Edge had been out on a simple stroll in the park when he had encountered you in this Lolita Meet Up that was stationed in the park. He had no idea what you were doing there, and since he had never seen you in a Lolita dress before, he thought you had been kidnapped into this party.

At first he couldn’t do anything because DEAR SWEET ASGORE YOU WERE SO CUTE BUT ALSO SUPER HOT SOMEONE HELP

Then you came over to him and oh wow, has he mentioned you look absolutely gorgeous in that dress

If you tell him that you didn’t want to embarrass him by admitting you were a Lolita, then YOU IN FOR A HECK TON OF AFFECTION, seriously, besides lasagna, you and cute things were his only weaknesses.

If you’re up for it, he’s going to request that you wear these Lolita dresses more often. It will take him a while to get used to having a frilled up lady on his arm, but darling you are worth it.

What especially gets him all flustered and unable to speak is if you find Lolita dresses in his colors (red and/or black) or Goth dresses. Even if you dress in the brightest pastel dresses ever, he’ll love you to bits.

It’s just seeing you wear something that clearly proclaims you are his gets him all flustered and in a puddle of absolute love for you that will result in him flaunting you to everyone he sees.


End file.
